- Email: [email protected]
Definition of an incombustible material
454
NATIONALBUREAUOF STANDARDSNOTES.
shift, and ‘temperature errors-are present day instruments are given.
[J. t:. I.
defined, and minimum values for
ALCOHOLAS AN ENGINEFUEL. In the Bureau’s studies of substitute fuels for possible use in parts of the world where petroleum is not readily available, engines have been operated on alcohol, both of conventional grade and in mixtures with water containing as little as 35 per cent. alcohol. The results emphasize the fact that the horsepower of an engine is fixed by the amount of air it gets, rather than the amount of fuel. With alcohol (190 proof), a given engine develops more horsepower by several per cent. than with gasoline, despite the fact that the heat available per pound from the alcohol is less than two-thirds as much as from the gasoline. The increased horsepower results from the fact that on vaporizing in the manifold the alcohol cools the air more than does the gasoline, thus permitting a greater weight of air to enter the cylinders. Although engine operation is possible with the very low-proof alcohols, disadvantages are: (I) the amounts of fuel used are so great that carburetor connections, jets, fuel lines, fuel pumps, and tanks would have to be increased in size; (2) large amounts of water collect in the engine crank case; (3) spark plugs become moist and fail to fire at low throttle. Spark settings must be changed and the fuel consumption, even based on the amount of alcohol alone, is double that for high-test alcohol. DEFINITIONOF AN INCOMBUSTIBLE MATERIAL. In building code and similar regulations it is necessary to define an incombustible material. A number of definitions are given in American building codes and one based on a specific testing procedure is given in British Standard 476-1932, “ British Standard Definitions for FireResistance, Incombustibility, and Non-Inflammability of Building The test for incombustibility involves Materials and Structures.” heating in a furnace up to a temperature of 750” C. (1382” F.) in I % hours. .It was found that the test, thus conducted, would class as incombustible some materials that contained a considerable percentage of combustible constituents and that had been indicated as a fire hazard when used in constructions such as chimneys. The procedure was modified by heating the furnace to 750” C. before introducing the specimen. This was found consistently to cause flaming and self-sustained glow in materials that have indicated any fire hazard in large-scale tests. For cellulosic materials, the maximum combustible content that can be present if it is to be classed as incombustible by this test, would be only a few per cent. Magnesium is
Ike..
lc)JJ.
1
NATIONAL
BUREAU
OF STANDARDS
NOTES.
455
indicated as combustible, whereas pure aluminum, even in finelypowdered form, is rated as incombustible. However, aluminum paint powder containing about 2 per cent. of oil and less than I per cent. of iron oxide, ignited readily. EXTERIOR PAINT ON TEMPORARY
ARMY
BUILDINGS.
The exteriors of the temporary buildings at Army cantonments were painted with two coats of paint (with some exceptions) 3% to 4 years ago. Some of the paint was a titanium-lead-zinc base, some was a lead-zinc base, and a small amount was pure white lead. The present condition of the exterior paint on buildings in various localities was inspected recently so that recommendations could be made concerning the repainting of those buildings that are to be kept in service during the post-war period. The results show that the climate affects the paint differently in different regions. For example, in the arid and sunny regions of the Southwest (for example, Fort Sill, Okla.), paint tends to become very brittle, and on such woods as southern yellow pine, the paint failure takes the form of cracking and flaking. In humid regions of the southern seaboard, paint fails mostly by chalking with little or no flaking. On the other hand, mildew may form on the painted surface in such climates. In the Northeast region, there is an in-between condition where there is usually enough dry weather to cause some flaking of paint on southern yellow pine but not so much as in arid regions. One interesting observation concerned the painting over knots in the wood. The majority of the buildings were built with The usual lumber of No. 2 common grade containing many knots. practice of shellacking the knots or of spotting them with aluminum paint did not prove of value. Therefore, for repainting, no special treatment (other than to scrape off any exudation) will be given the knots. SPECTROPHOTOMETERS.
Quantitative chemical analysis is often a time-consuming task, and the industrial chemist is always interested in short-cut methods. One of these more rapid methods makes use of the color inherent in a solution, or which is produced in many solutions when mixed or treated with certain other chemicals. This color is caused by .absorption of light in a region of the spectrum having a color more or less complimentary to that of the solution itself. If, then, the chemist has available a precise method of measuring this absorption of light, he can determine the, amount of absorbing material in the solution with considerable precision. The spectrophotometer is an instrument that will measure the absorption of light in solutions. Such instruments have been used for
NATIONALBUREAUOF STANDARDSNOTES.
shift, and ‘temperature errors-are present day instruments are given.
[J. t:. I.
defined, and minimum values for
ALCOHOLAS AN ENGINEFUEL. In the Bureau’s studies of substitute fuels for possible use in parts of the world where petroleum is not readily available, engines have been operated on alcohol, both of conventional grade and in mixtures with water containing as little as 35 per cent. alcohol. The results emphasize the fact that the horsepower of an engine is fixed by the amount of air it gets, rather than the amount of fuel. With alcohol (190 proof), a given engine develops more horsepower by several per cent. than with gasoline, despite the fact that the heat available per pound from the alcohol is less than two-thirds as much as from the gasoline. The increased horsepower results from the fact that on vaporizing in the manifold the alcohol cools the air more than does the gasoline, thus permitting a greater weight of air to enter the cylinders. Although engine operation is possible with the very low-proof alcohols, disadvantages are: (I) the amounts of fuel used are so great that carburetor connections, jets, fuel lines, fuel pumps, and tanks would have to be increased in size; (2) large amounts of water collect in the engine crank case; (3) spark plugs become moist and fail to fire at low throttle. Spark settings must be changed and the fuel consumption, even based on the amount of alcohol alone, is double that for high-test alcohol. DEFINITIONOF AN INCOMBUSTIBLE MATERIAL. In building code and similar regulations it is necessary to define an incombustible material. A number of definitions are given in American building codes and one based on a specific testing procedure is given in British Standard 476-1932, “ British Standard Definitions for FireResistance, Incombustibility, and Non-Inflammability of Building The test for incombustibility involves Materials and Structures.” heating in a furnace up to a temperature of 750” C. (1382” F.) in I % hours. .It was found that the test, thus conducted, would class as incombustible some materials that contained a considerable percentage of combustible constituents and that had been indicated as a fire hazard when used in constructions such as chimneys. The procedure was modified by heating the furnace to 750” C. before introducing the specimen. This was found consistently to cause flaming and self-sustained glow in materials that have indicated any fire hazard in large-scale tests. For cellulosic materials, the maximum combustible content that can be present if it is to be classed as incombustible by this test, would be only a few per cent. Magnesium is
Ike..
lc)JJ.
1
NATIONAL
BUREAU
OF STANDARDS
NOTES.
455
indicated as combustible, whereas pure aluminum, even in finelypowdered form, is rated as incombustible. However, aluminum paint powder containing about 2 per cent. of oil and less than I per cent. of iron oxide, ignited readily. EXTERIOR PAINT ON TEMPORARY
ARMY
BUILDINGS.
The exteriors of the temporary buildings at Army cantonments were painted with two coats of paint (with some exceptions) 3% to 4 years ago. Some of the paint was a titanium-lead-zinc base, some was a lead-zinc base, and a small amount was pure white lead. The present condition of the exterior paint on buildings in various localities was inspected recently so that recommendations could be made concerning the repainting of those buildings that are to be kept in service during the post-war period. The results show that the climate affects the paint differently in different regions. For example, in the arid and sunny regions of the Southwest (for example, Fort Sill, Okla.), paint tends to become very brittle, and on such woods as southern yellow pine, the paint failure takes the form of cracking and flaking. In humid regions of the southern seaboard, paint fails mostly by chalking with little or no flaking. On the other hand, mildew may form on the painted surface in such climates. In the Northeast region, there is an in-between condition where there is usually enough dry weather to cause some flaking of paint on southern yellow pine but not so much as in arid regions. One interesting observation concerned the painting over knots in the wood. The majority of the buildings were built with The usual lumber of No. 2 common grade containing many knots. practice of shellacking the knots or of spotting them with aluminum paint did not prove of value. Therefore, for repainting, no special treatment (other than to scrape off any exudation) will be given the knots. SPECTROPHOTOMETERS.
Quantitative chemical analysis is often a time-consuming task, and the industrial chemist is always interested in short-cut methods. One of these more rapid methods makes use of the color inherent in a solution, or which is produced in many solutions when mixed or treated with certain other chemicals. This color is caused by .absorption of light in a region of the spectrum having a color more or less complimentary to that of the solution itself. If, then, the chemist has available a precise method of measuring this absorption of light, he can determine the, amount of absorbing material in the solution with considerable precision. The spectrophotometer is an instrument that will measure the absorption of light in solutions. Such instruments have been used for